上海交通大学：《生物与机器人学》课程教学资源_Medical Robotics and Computer-Integrated Surgery

199 52.Medical Robotics and Computer-Integrated Surgery Russell H.Taylor,Arianna Menciassi,Gabor Fichtinger,Paolo Dario The growth of medical robotics since the mid- 52.1 Core concepts....1200 1980s has been striking.From a few initial efforts 52.1.1 Medical Robotics, in stereotactic brain surgery,orthopaedics,endo- Computer-Integrated Surgery, and Closed-Loop Interventions......1200 scopic surgery,microsurgery,and other areas,the 52.1.2 Factors Affecting the Acceptance field has expanded to include commercially mar- of Medical Robots.......... ..1200 keted,clinically deployed systems,and a robust 52.1.3 Medical Robotics System m and exponentially expanding research community. Paradigms:Surgical CAD/CAM u This chapter will discuss some major themes and and Surgical Assistance...............1202 illustrate them with examples from current and past research.Further reading providing a more 52.2 Technology.............. .1204 comprehensive review of this rapidly expanding 52.2.1 Mechanical Design Considerations..1204 field is suggested in Sect.52.4. 52.2.2 Control Paradigms 1205 Medical robots may be classified in many ways: 52.2.3 Virtual Fixtures by manipulator design (e.g.,kinematics,actua- and Human-Machine tion);by level of autonomy (e.g.,preprogrammed Cooperative Systems................1206 52.2.4 Safety and Sterility........ ....1207 versus teleoperation versus constrained cooper- 52.2.5 Imaging and Modeling ative control),by targeted anatomy or technique of Patients...... .1208 (e.g.,cardiac,intravascular,percutaneous,la- 52.2.6 Registration. 1208 paroscopic,microsurgical);or intended operating environment(e.g.,in-scanner,conventional op- 52.3 Systems,Research Areas, erating room).In this chapter,we have chosen to and Applications............ .1209 focus on the role of medical robots within the con- 52.3.1 Nonrobotic Computer-Assisted text of larger computer-integrated systems includ- Surgery:Navigation ing presurgical planning,intraoperative execution, and Image Overlay Devices .1209 and postoperative assessment and follow-up. 52.3.2 Orthopaedic Systems .1209 First,we introduce basic concepts of computer- 52.3.3 Percutaneous Needle integrated surgery,discuss critical factors affecting Placement Systems...... ..1210 the eventual deployment and acceptance of 52.3.4Telesurgical Systems .1212 medical robots,and introduce the basic system 52.3.5 Microsurgery Systems.113 52.3.6 Endoluminal Robots. paradigms of surgical computer-assisted plan- .1213 52.3.7 Sensorized Instruments ning,registration,execution,monitoring,and and Haptic Feedback 1214 assessment(CAD/CAM)and surgical assistance.In 52.3.8 Surgical Simulators subsequent sections,we provide an overview of and Telerobotic Systems the technology of medical robot systems and dis- for Training..... 1215 cuss examples of our basic system paradigms, 52.3.9 0ther Applications with brief additional discussion topics of remote and Research Areas 1216 telesurgery and robotic surgical simulators.We conclude with some thoughts on future research 52.4 Conclusion and Future Directions...........1217 directions and provide suggested further reading. Reference5.… 1218

1199 Medical Robo 52. Medical Robotics and Computer-Integrated Surgery Russell H. Taylor, Arianna Menciassi, Gabor Fichtinger, Paolo Dario The growth of medical robotics since the mid- 1980s has been striking. From a few initial efforts in stereotactic brain surgery, orthopaedics, endo￾scopic surgery, microsurgery, and other areas, the field has expanded to include commercially mar￾keted, clinically deployed systems, and a robust and exponentially expanding research community. This chapter will discuss some major themes and illustrate them with examples from current and past research. Further reading providing a more comprehensive review of this rapidly expanding field is suggested in Sect. 52.4. Medical robots may be classified in many ways: by manipulator design (e.g., kinematics, actua￾tion); by level of autonomy (e.g., preprogrammed versus teleoperation versus constrained cooper￾ative control), by targeted anatomy or technique (e.g., cardiac, intravascular, percutaneous, la￾paroscopic, microsurgical); or intended operating environment (e.g., in-scanner, conventional op￾erating room). In this chapter, we have chosen to focus on the role of medical robots within the con￾text of larger computer-integrated systems includ￾ing presurgical planning, intraoperative execution, and postoperative assessment and follow-up. First, we introduce basic concepts of computer￾integrated surgery, discuss critical factors affecting the eventual deployment and acceptance of medical robots, and introduce the basic system paradigms of surgical computer-assisted plan￾ning, registration, execution, monitoring, and assessment (CAD/CAM) and surgical assistance. In subsequent sections, we provide an overview of the technology of medical robot systems and dis￾cuss examples of our basic system paradigms, with brief additional discussion topics of remote telesurgery and robotic surgical simulators. We conclude with some thoughts on future research directions and provide suggested further reading. 52.1 Core Concepts ....................................... 1200 52.1.1 Medical Robotics, Computer-Integrated Surgery, and Closed-Loop Interventions ...... 1200 52.1.2 Factors Affecting the Acceptance of Medical Robots......................... 1200 52.1.3 Medical Robotics System Paradigms: Surgical CAD/CAM and Surgical Assistance ................. 1202 52.2 Technology .......................................... 1204 52.2.1 Mechanical Design Considerations .. 1204 52.2.2 Control Paradigms ........................ 1205 52.2.3 Virtual Fixtures and Human–Machine Cooperative Systems ..................... 1206 52.2.4 Safety and Sterility ....................... 1207 52.2.5 Imaging and Modeling of Patients .................................. 1208 52.2.6 Registration................................. 1208 52.3 Systems, Research Areas, and Applications .................................. 1209 52.3.1 Nonrobotic Computer-Assisted Surgery: Navigation and Image Overlay Devices ............ 1209 52.3.2 Orthopaedic Systems .................... 1209 52.3.3 Percutaneous Needle Placement Systems ....................... 1210 52.3.4 Telesurgical Systems ..................... 1212 52.3.5 Microsurgery Systems.................... 1213 52.3.6 Endoluminal Robots ..................... 1213 52.3.7 Sensorized Instruments and Haptic Feedback .................... 1214 52.3.8Surgical Simulators and Telerobotic Systems for Training ................................. 1215 52.3.9Other Applications and Research Areas ...................... 1216 52.4 Conclusion and Future Directions ........... 1217 References .................................................. 1218 Part F 52

1200 Part F Field and Service Robotics 52.1 Core Concepts 52.1.1 Medical Robotics, Figure 52.1 illustrates this view of computer- Computer-Integrated Surgery, integrated surgery (CIS).The process starts with and Closed-Loop Interventions information about the patient,which can include medical images [computed tomography (CT).magnetic reso- A fundamental property of robotic systems is their abil- nance imaging (MRD),positron emission tomography ity to couple complex information to physical action (PET),etc.],lab test results,and other information.This in order to perform a useful task.This ability to re- patient-specific information is combined with statisti- place,supplement,or transcend human performance has cal information about human anatomy,physiology,and had a profound influence on many fields of our soci- disease to produce a comprehensive computer represen- ety,including industrial production,exploration,quality tation of the patient,which can then be used to produce control,and laboratory processes.Although robots have an optimized interventional plan.In the operating room, Part often been first introduced to automate or improve dis- the preoperative patient model and plan must be reg- crete processes such as welding or test probe placement istered to the actual patient.Typically,this is done by F-52 or to provide access to environments where humans identifying corresponding landmarks or structures on the cannot safely go,their greater long-term impact has of- preoperative model and the patient,either by means of ten come indirectly as essential enablers of computer additional imaging (X-ray,ultrasound,video),by the use integration of entire production or service processes. of a tracked pointing device,or by the robot itself.If the Medical robots have a similar potential to funda- patient's anatomy has changed,then the model and plan mentally change surgery and interventional medicine are updated appropriately,and the planned procedure is as part of a broader,information-intensive environment carried out with assistance of the robot.As the interven- that exploits the complementary strengths of humans and tion continues,additional imaging or other sensing is computer-based technology.The robots may be thought used to monitor the progress of the procedure,to update of as information-driven surgical tools that enable hu- the patient model,and to verify that the planned proce- man surgeons to treat individual patients with greater dure has been successfully executed.After the procedure safety,improved efficacy,and reduced morbidity than is complete,further imaging,modeling,and computer- would otherwise be possible.Further,the consistency assisted assessment is performed for patient follow-up and information infrastructure associated with medical and to plan subsequent interventions,if any should be robotic and computer-assisted surgery systems have the required.Further,all the patient-specific data generated potential to make computer-integrated surgery as impor- during the planning,execution,and follow-up phases tant to health care as computer-integrated manufacturing can be retained.These data can subsequently be an- is to industrial production. alyzed statistically to improve the rules and methods used to plan future procedures. Information 52.1.2 Factors Affecting the Acceptance of Medical Robots Patient-specific information (images,lab results Model Plan Medical robotics is ultimately an application-driven genetics.text Acton research field.Although the development of medical records,etc.) robotic systems requires significant innovation and can lead to very real,fundamental advances in technology, medical robots must provide measurable and significant General information (anatomic atlases. Patient-specific evaluation advantages if they are to be widely accepted and de- statistics,rules) ployed.The situation is complicated by the fact that these advantages are often difficult to measure,can take an extended period to assess,and may be of varying im- Statistical analysis portance to different groups.Table 52.1 lists some of the more important factors that researchers contemplating Fig.52.1 Fundamental information flow in computer-integrated the development of a new medical robot system should surgery consider in assessing their proposed approach

1200 Part F Field and Service Robotics 52.1 Core Concepts 52.1.1 Medical Robotics, Computer-Integrated Surgery, and Closed-Loop Interventions A fundamental property of robotic systems is their abil￾ity to couple complex information to physical action in order to perform a useful task. This ability to re￾place, supplement, or transcend human performance has had a profound influence on many fields of our soci￾ety, including industrial production, exploration, quality control, and laboratory processes. Although robots have often been first introduced to automate or improve dis￾crete processes such as welding or test probe placement or to provide access to environments where humans cannot safely go, their greater long-term impact has of￾ten come indirectly as essential enablers of computer integration of entire production or service processes. Medical robots have a similar potential to funda￾mentally change surgery and interventional medicine as part of a broader, information-intensive environment that exploits the complementary strengths of humans and computer-based technology. The robots may be thought of as information-driven surgical tools that enable hu￾man surgeons to treat individual patients with greater safety, improved efficacy, and reduced morbidity than would otherwise be possible. Further, the consistency and information infrastructure associated with medical robotic and computer-assisted surgery systems have the potential to make computer-integrated surgery as impor￾tant to health care as computer-integrated manufacturing is to industrial production. Information Statistical analysis Patient-specific evaluation Model Plan Action Patient-specific information (images, lab results, genetics, text records, etc.) General information (anatomic atlases, statistics, rules) Fig. 52.1 Fundamental information flow in computer-integrated surgery Figure 52.1 illustrates this view of computer￾integrated surgery (CIS). The process starts with information about the patient, which can include medical images [computed tomography (CT), magnetic reso￾nance imaging (MRI), positron emission tomography (PET), etc.], lab test results, and other information. This patient-specific information is combined with statisti￾cal information about human anatomy, physiology, and disease to produce a comprehensive computer represen￾tation of the patient, which can then be used to produce an optimized interventional plan. In the operating room, the preoperative patient model and plan must be reg￾istered to the actual patient. Typically, this is done by identifying corresponding landmarks or structures on the preoperative model and the patient, either by means of additional imaging (X-ray, ultrasound, video), by the use of a tracked pointing device, or by the robot itself. If the patient’s anatomy has changed, then the model and plan are updated appropriately, and the planned procedure is carried out with assistance of the robot. As the interven￾tion continues, additional imaging or other sensing is used to monitor the progress of the procedure, to update the patient model, and to verify that the planned proce￾dure has been successfully executed. After the procedure is complete, further imaging, modeling, and computer￾assisted assessment is performed for patient follow-up and to plan subsequent interventions, if any should be required. Further, all the patient-specific data generated during the planning, execution, and follow-up phases can be retained. These data can subsequently be an￾alyzed statistically to improve the rules and methods used to plan future procedures. 52.1.2 Factors Affecting the Acceptance of Medical Robots Medical robotics is ultimately an application-driven research field. Although the development of medical robotic systems requires significant innovation and can lead to very real, fundamental advances in technology, medical robots must provide measurable and significant advantages if they are to be widely accepted and de￾ployed. The situation is complicated by the fact that these advantages are often difficult to measure, can take an extended period to assess, and may be of varying im￾portance to different groups. Table 52.1 lists some of the more important factors that researchers contemplating the development of a new medical robot system should consider in assessing their proposed approach. Part F 52.1

Medical Robotics and Computer-Integrated Surgery 52.1 Core Concepts 1201 Table 52.1 Assessment factors for medical robots or computer-integrated surgery systems [52.1] Assessment factor Important to whom Assessment method Summary of key leverage New treatment Clinical researchers, Clinical and trials Transcend human sensory-motor limits options patients preclinical (e.g.,in microsurgery).Enable less invasive procedures with real-time image feedback (e.g..fluoroscopic or MRI-guided liver or prostate therapy).Speed up clinical research through greater consistency and data gathering Quality Surgeons. Clinician Significantly improve the quality of surgical technique (e.g.. patients judgment; in microvascular anastomosis),thus improving results and revision rates reducing the need for revision surgery Time and cost Surgeons, Hours, Speed operating room(OR)time for some interventions.Reduce hospitals, hospital costs from healing time and revision surgery.Provide effective insurers charges intervention to treat patient condition Less Surgeons, Qualitative Provide crucial information and feedback needed to reduce Part invasiveness patients judgment: the invasiveness of surgical procedures,thus reducing recovery times infection risk,recovery times,and costs(e.g..percutaneous spine surgery) Safety Surgeons. Complication Reduce surgical complications and errors,again lowering patients and revision costs,improving outcomes and shortening hospital stays surgery rates (e.g.,robotic total hip replacement(THR),steady-hand brain surgery) Real-time Surgeons Qualitative Integrate preoperative models and intraoperative images to feedback assessment, give surgeon timely and accurate information about the quantitative patient and intervention(e.g.,fluoroscopic X-rays without comparison of surgeon exposure,percutaneous therapy in conventional plan to MRI scanners).Assure that the planned intervention has in observation. fact been accomplished revision surgery rates Accuracy or Surgeons Quantitative Significantly improve the accuracy of therapy dose pattern precision comparison of delivery and tissue manipulation tasks (e.g.,solid organ plan to actual therapy,microsurgery,robotic bone machining) Enhanced Surgeons, Databases, Exploit CIS systems'ability to log more varied and detailed documentation clinical anatomical information about each surgical case than is practical in and follow-up researchers atlases. conventional manual surgery.Over time,this ability. images,and coupled with CIS systems'consistency,has the potential to clinical significantly improve surgical practice and shorten research observations trials Broadly,the advantages offered by medical robots These capabilities can both enhance the ability of an av- may be grouped into three areas.The first is the poten- erage surgeon to perform procedures that only a few tial of a medical robot to significantly improve surgeons' exceptionally gifted surgeons can perform unassisted technical capabiliry to perform procedures by exploiting and can also make it possible to perform interventions the complementary strengths of humans and robots sum-that would otherwise be completely infeasible. marized in Table 52.2.Medical robots can be constructed A second,closely related capability is the poten- to be more precise and geometrically accurate than an tial of medical robots to promote surgical safery both unaided human.They can operate in hostile radiolog-by improving a surgeon's technical performance and by ical environments and can provide great dexterity for means of active assists such as no-fly zones or virtual minimally invasive procedures inside the patient's body.fixtures (Sect.52.2.3)to prevent surgical instruments

Medical Robotics and Computer-Integrated Surgery 52.1 Core Concepts 1201 Table 52.1 Assessment factors for medical robots or computer-integrated surgery systems [52.1] Assessment factor Important to whom Assessment method Summary of key leverage New treatment Clinical researchers, Clinical and trials Transcend human sensory-motor limits options patients preclinical (e.g., in microsurgery). Enable less invasive procedures with real-time image feedback (e.g., fluoroscopic or MRI-guided liver or prostate therapy). Speed up clinical research through greater consistency and data gathering Quality Surgeons, Clinician Significantly improve the quality of surgical technique (e.g., patients judgment; in microvascular anastomosis), thus improving results and revision rates reducing the need for revision surgery Time and cost Surgeons, Hours, Speed operating room (OR) time for some interventions. Reduce hospitals, hospital costs from healing time and revision surgery. Provide effective insurers charges intervention to treat patient condition Less Surgeons, Qualitative Provide crucial information and feedback needed to reduce invasiveness patients judgment; the invasiveness of surgical procedures, thus reducing recovery times infection risk, recovery times, and costs (e.g., percutaneous spine surgery) Safety Surgeons, Complication Reduce surgical complications and errors, again lowering patients and revision costs, improving outcomes and shortening hospital stays surgery rates (e.g., robotic total hip replacement (THR), steady-hand brain surgery) Real-time Surgeons Qualitative Integrate preoperative models and intraoperative images to feedback assessment, give surgeon timely and accurate information about the quantitative patient and intervention (e.g., fluoroscopic X-rays without comparison of surgeon exposure, percutaneous therapy in conventional plan to MRI scanners). Assure that the planned intervention has in observation, fact been accomplished revision surgery rates Accuracy or Surgeons Quantitative Significantly improve the accuracy of therapy dose pattern precision comparison of delivery and tissue manipulation tasks (e.g., solid organ plan to actual therapy, microsurgery, robotic bone machining) Enhanced Surgeons, Databases, Exploit CIS systems’ ability to log more varied and detailed documentation clinical anatomical information about each surgical case than is practical in and follow-up researchers atlases, conventional manual surgery. Over time, this ability, images, and coupled with CIS systems’ consistency, has the potential to clinical significantly improve surgical practice and shorten research observations trials Broadly, the advantages offered by medical robots may be grouped into three areas. The first is the poten￾tial of a medical robot to significantly improve surgeons’ technical capability to perform procedures by exploiting the complementary strengths of humans and robots sum￾marized in Table 52.2. Medical robots can be constructed to be more precise and geometrically accurate than an unaided human. They can operate in hostile radiolog￾ical environments and can provide great dexterity for minimally invasive procedures inside the patient’s body. These capabilities can both enhance the ability of an av￾erage surgeon to perform procedures that only a few exceptionally gifted surgeons can perform unassisted and can also make it possible to perform interventions that would otherwise be completely infeasible. A second, closely related capability is the poten￾tial of medical robots to promote surgical safety both by improving a surgeon’s technical performance and by means of active assists such as no-fly zones or virtual fixtures (Sect. 52.2.3) to prevent surgical instruments Part F 52.1

1202 Part F Field and Service Robotics Table 52.2 Complementary strengths of human surgeons and robots [52.1] Strengths Limitations Humans Excellent judgment Prone to fatigue and inattention Excellent hand-eye coordination Limited fine motion control due to tremor Excellent dexterity (at natural hmnan scale) Limited manipulation ability and dexterity Able to integrate and act on multiple information outside natural scale sources Cannot see through tissue Easily trained Bulky end-effectors(hands) Versatile and able to improvise Limited geometric accuracy Hard to keep sterile Affected by radiation.infection Robots Excellent geometric accuracy Poor judgment Untiring and stable Hard to adapt to new situations Part F52.1 Immune to ionizing radiation Limited dexterity Can be designed to operate at Limited hand-eye coordination many different scales of motion Limited haptic sensing(today) and payload Limited ability to integrate and Able to integrate multiple sources interpret complex information of numerical and sensor data from causing unintentional damage to delicate struc- ing of sutures or in placing of components in joint recon- tures.Furthermore,the integration of medical robots structions)is itself an important quality factor.If saved within the information infrastructure of a larger CIS and routinely analyzed,the flight data recorder infor- system can provide the surgeon with significantly im- mation inherently available with a medical robot can be proved monitoring and online decision supports,thus used both in morbidiry and mortaliry assessments of seri- further improving safety. ous surgical incidents and,potentially,in statistical anal- A third advantage is the inherent ability of medical yses examining many cases to develop better surgical robots and CIS systems to promote consistency while plans.Furthermore,such data can provide valuable input capturing detailed online information for every proce- for surgical simulators,as well as a database for develop- dure.Consistent execution(e.g.,in spacing and tension-ing skill assessment and certification tools for surgeons. Stereo video Fig.52.2 The daVinci telesurgical Instrument robot [52.2]extends a surgeon's ca- manipulators pabilities by providing the immediacy Surgeon interface and dexterity of open surgery in manipulators Motion controller a minimally invasive surgical envi- ronment.(Photos:Intuitive Surgical. Sunnyvale)

1202 Part F Field and Service Robotics Table 52.2 Complementary strengths of human surgeons and robots [52.1] Strengths Limitations Humans Excellent judgment Prone to fatigue and inattention Excellent hand–eye coordination Limited fine motion control due to tremor Excellent dexterity (at natural human scale) Limited manipulation ability and dexterity Able to integrate and act on multiple information outside natural scale sources Cannot see through tissue Easily trained Bulky end-effectors (hands) Versatile and able to improvise Limited geometric accuracy Hard to keep sterile Affected by radiation, infection Robots Excellent geometric accuracy Poor judgment Untiring and stable Hard to adapt to new situations Immune to ionizing radiation Limited dexterity Can be designed to operate at Limited hand–eye coordination many different scales of motion Limited haptic sensing (today) and payload Limited ability to integrate and Able to integrate multiple sources interpret complex information of numerical and sensor data from causing unintentional damage to delicate struc￾tures. Furthermore, the integration of medical robots within the information infrastructure of a larger CIS system can provide the surgeon with significantly im￾proved monitoring and online decision supports, thus further improving safety. A third advantage is the inherent ability of medical robots and CIS systems to promote consistency while capturing detailed online information for every proce￾dure. Consistent execution (e.g., in spacing and tension￾Stereo video Instrument manipulators Surgeon interface manipulators Motion controller Fig. 52.2 The daVinci telesurgical robot [52.2] extends a surgeon’s ca￾pabilities by providing the immediacy and dexterity of open surgery in a minimally invasive surgical envi￾ronment. (Photos: Intuitive Surgical, Sunnyvale) ing of sutures or in placing of components in joint recon￾structions) is itself an important quality factor. If saved and routinely analyzed, the flight data recorder infor￾mation inherently available with a medical robot can be used both in morbidity and mortality assessments of seri￾ous surgical incidents and, potentially, in statistical anal￾yses examining many cases to develop better surgical plans. Furthermore, such data can provide valuable input for surgical simulators, as well as a database for develop￾ing skill assessment and certification tools for surgeons. Part F 52.1

Medical Robotics and Computer-Integrated Surgery 52.1 Core Concepts 1203 52.1.3 Medical Robotics System Paradigms: orthopaedic joint reconstructions(discussed further in Surgical CAD/CAM Sect.52.3.2)and image-guided placement of therapy and Surgical Assistance needles (Sect.52.3.3). Surgery is often highly interactive;many decisions We call the process of computer-assisted planning,regis- are made by the surgeon in the operating room and exe- tration,execution,monitoring,and assessment surgical cuted immediately,usually with direct visual or haptic CAD/CAM,emphasizing the analogy to manufacturing feedback.Generally,the goal of surgical robotics is not CAD/CAM.Just as with manufacturing,robots can be to replace the surgeon so much as to improve his or her critical in this CAD/CAM process by enhancing the ability to treat the patient.The robot is thus a computer- surgeon's ability to execute surgical plans.The spe-controlled surgical tool in which control of the robot is cific role played by the robot depends somewhat on often shared in one way or another between the human the application,but current systems tend to exploit surgeon and a computer.We thus often speak of medical the geometric accuracy of the robot and/or its ability robots as surgical assistants. to function concurrently with X-ray or other imag- Broadly,robotic surgical assistants may be broken ing devices.Typical examples include radiation therapy into two subcategories.The first category,surgeon ex- delivery robots such as Accuray's CyberKnife [52.5] tender robots.manipulate surgical instruments under the (Accuray,Inc.,Sunnyvale,CA.),shaping of bone in direct control of the surgeon,usually through a teleop- Part F52 a) b) Stereo display Microscope C.n(任handte-Cscale frool） Tool handle Cameras Robot interface Optional HMD Steady hand robot Fig.52.3a,b The Johns Hopkins Steady Hand microsurgical robot [52.3,4]extends a surgeon's capabilities by providing the ability to manipulate surgical instruments with very high precision while still exploiting the surgeon's natural hand-eye coordination.(a)The basic paradigm of hands-on compliant guiding.The commanded velocity of the robot is proportional to a scaled difference between the forces exerted by the surgeon on the tool handle and (optionally)sensed tool-to-tissue forces.(b)A more recent version of the Steady Hand robot currently being used for experiments in microcannulation of l00μn blood vessels

Medical Robotics and Computer-Integrated Surgery 52.1 Core Concepts 1203 52.1.3 Medical Robotics System Paradigms: Surgical CAD/CAM and Surgical Assistance We call the process of computer-assisted planning, regis￾tration, execution, monitoring, and assessment surgical CAD/CAM, emphasizing the analogy to manufacturing CAD/CAM. Just as with manufacturing, robots can be critical in this CAD/CAM process by enhancing the surgeon’s ability to execute surgical plans. The spe￾cific role played by the robot depends somewhat on the application, but current systems tend to exploit the geometric accuracy of the robot and/or its ability to function concurrently with X-ray or other imag￾ing devices. Typical examples include radiation therapy delivery robots such as Accuray’s CyberKnife [52.5] (Accuray, Inc., Sunnyvale, CA.), shaping of bone in fhandle a) b) Stereo display Microscope Tool Cameras Optional HMD Steady hand robot x · f cmd tool Robot interface Cυ (fhandle – Cscale ftool) Fig. 52.3a,b The Johns Hopkins Steady Hand microsurgical robot [52.3,4] extends a surgeon’s capabilities by providing the ability to manipulate surgical instruments with very high precision while still exploiting the surgeon’s natural hand–eye coordination. (a) The basic paradigm of hands-on compliant guiding. The commanded velocity of the robot is proportional to a scaled difference between the forces exerted by the surgeon on the tool handle and (optionally) sensed tool-to-tissue forces. (b) A more recent version of the Steady Hand robot currently being used for experiments in microcannulation of 100μm blood vessels orthopaedic joint reconstructions (discussed further in Sect. 52.3.2) and image-guided placement of therapy needles (Sect. 52.3.3). Surgery is often highly interactive; many decisions are made by the surgeon in the operating room and exe￾cuted immediately, usually with direct visual or haptic feedback. Generally, the goal of surgical robotics is not to replace the surgeon so much as to improve his or her ability to treat the patient. The robot is thus a computer￾controlled surgical tool in which control of the robot is often shared in one way or another between the human surgeon and a computer. We thus often speak of medical robots as surgical assistants. Broadly, robotic surgical assistants may be broken into two subcategories. The first category, surgeon ex￾tender robots, manipulate surgical instruments under the direct control of the surgeon, usually through a teleop￾Part F 52.1

1204 Part F Field and Service Robotics eration or hands-on cooperative control interface.The positioning.or endoscope holding.One primary advan- primary value of these systems is that they can overcome tage of such systems is their potential to reduce the some of the perception and manipulation limitations of number of people required in the operating room,al- the surgeon.Examples include the ability to manipu- though that advantage can only be achieved if all the late surgical instruments with superhuman precision by tasks routinely performed by an assisting individual can eliminating hand tremor,the ability to perform highly be automated.Other advantages can include improved dexterous tasks inside the patient's body,or the abil-task performance (e.g.,a steadier endoscopic view), ity to perform surgery on a patient who is physically safety (e.g.,elimination of excessive retraction forces), remote from the surgeon.Although setup time is still or simply giving the surgeon a greater feeling of control a serious concern with most surgeon extender systems, over the procedure.One of the key challenges in these the greater ease of manipulation that such systems offer systems is providing the required assistance without pos- has the potential to reduce operative times.One widely ing an undue burden on the surgeon's attention.A variety deployed example of a surgeon extender is the daVinci of control interfaces are common,including joysticks, Part system [52.2](Intuitive Surgical Systems,Sunnyvale,head tracking,voice recognition systems,and visual CA)shown in Fig.52.2.Other examples include the tracking of the surgeon and surgical instruments,for ex- Sensei cathetersystem [52.6](Hansen Medical Systems,ample,the Aesop endoscope positioner[52.7]used both u Mountain View,CA.)and the experimental Johns Hop- a foot-actuated joystick and a very effective voice recog- kins University (JHU)Steady Hand microsurgery robot nition system.Again,further examples are discussed in shown in Fig.52.3.Further examples are discussed in Sect.52.3. Sect.52.3. It is important to realize that surgical CAD/CAM A second category,auxiliary surgical support and surgical assistance are complementary concepts. robots,generally work alongside the surgeon and per- They are not at all incompatible,and many systems have form such routine tasks as tissue retraction,limb aspects of both. 52.2 Technology 52.2.1 Mechanical Design Considerations designs.For example,laparoscopic surgery and percu- taneous needle placement procedures typically involve The mechanical design of a surgical robot depends cru- the passage or manipulation of instruments about a com- cially on its intended application.For example,robots mon entry point into the patient's body.There are two with high precision,stiffness and (possibly)limited basic design approaches.The first approach uses a pas- dexterity are often very suitable for orthopaedic bone sive wrist to allow the instrument to pivot about the shaping or stereotactic needle placement,and medical insertion point and has been used in the commercial robots for these applications [52.8-11]frequently have Aesop and Zeus robots [52.12,14]as well as several high gear ratios and consequently,low back-drivability, research systems.The second approach mechanically high stiffness,and low speed.On the other hand,robots constrains the motion of the surgical tool to rotate about for complex,minimally invasive surgery (MIS)on soft a remote center of motion (RCM)distal to the robot's tissues require compactness,dexterity,and responsive- structure.In surgery,the robot is positioned so that ness.These systems [52.2,12]frequently have relatively the RCM point coincides with the entry point into the high speed,low stiffness,and highly back-drivable patient's body.This approach has been used by the com- mechanisms. mercially developed daVinci robot [52.21,as well as by Many early medical robots [52.8,11,13]were es- numerous research groups,using a variety of kinematic sentially modified industrial robots.This approach has designs [52.15-171. many advantages,including low cost,high reliability, The emergence of minimally invasive surgery has and shortened development times.If suitable modifica-created a need for robotic systems that can provide tions are made to ensure safety and sterility,such systems high degrees of dexterity in very constrained spaces can be very successful clinically [52.9],and they can also inside the patient's body,and at smaller and smaller be invaluable for rapid prototyping and research use. scales.Figure 52.4 shows several typical examples of However,the specialized requirements of surgical current approaches.One common response has been to applications have tended to encourage more specialized develop cable-actuated wrists [52.2].However,a num-

1204 Part F Field and Service Robotics eration or hands-on cooperative control interface. The primary value of these systems is that they can overcome some of the perception and manipulation limitations of the surgeon. Examples include the ability to manipu￾late surgical instruments with superhuman precision by eliminating hand tremor, the ability to perform highly dexterous tasks inside the patient’s body, or the abil￾ity to perform surgery on a patient who is physically remote from the surgeon. Although setup time is still a serious concern with most surgeon extender systems, the greater ease of manipulation that such systems offer has the potential to reduce operative times. One widely deployed example of a surgeon extender is the daVinci system [52.2] (Intuitive Surgical Systems, Sunnyvale, CA) shown in Fig. 52.2. Other examples include the Sensei catheter system [52.6] (Hansen Medical Systems, Mountain View, CA.) and the experimental Johns Hop￾kins University (JHU) Steady Hand microsurgery robot shown in Fig. 52.3. Further examples are discussed in Sect. 52.3. A second category, auxiliary surgical support robots, generally work alongside the surgeon and per￾form such routine tasks as tissue retraction, limb positioning, or endoscope holding. One primary advan￾tage of such systems is their potential to reduce the number of people required in the operating room, al￾though that advantage can only be achieved if all the tasks routinely performed by an assisting individual can be automated. Other advantages can include improved task performance (e.g., a steadier endoscopic view), safety (e.g., elimination of excessive retraction forces), or simply giving the surgeon a greater feeling of control over the procedure. One of the key challenges in these systems is providing the required assistance without pos￾ing an undue burden on the surgeon’s attention. A variety of control interfaces are common, including joysticks, head tracking, voice recognition systems, and visual tracking of the surgeon and surgical instruments, for ex￾ample, the Aesop endoscope positioner [52.7] used both a foot-actuated joystick and a very effective voice recog￾nition system. Again, further examples are discussed in Sect. 52.3. It is important to realize that surgical CAD/CAM and surgical assistance are complementary concepts. They are not at all incompatible, and many systems have aspects of both. 52.2 Technology 52.2.1 Mechanical Design Considerations The mechanical design of a surgical robot depends cru￾cially on its intended application. For example, robots with high precision, stiffness and (possibly) limited dexterity are often very suitable for orthopaedic bone shaping or stereotactic needle placement, and medical robots for these applications [52.8–11] frequently have high gear ratios and consequently, low back-drivability, high stiffness, and low speed. On the other hand, robots for complex, minimally invasive surgery (MIS) on soft tissues require compactness, dexterity, and responsive￾ness. These systems [52.2,12] frequently have relatively high speed, low stiffness, and highly back-drivable mechanisms. Many early medical robots [52.8, 11, 13] were es￾sentially modified industrial robots. This approach has many advantages, including low cost, high reliability, and shortened development times. If suitable modifica￾tions are made to ensure safety and sterility, such systems can be very successful clinically [52.9], and they can also be invaluable for rapid prototyping and research use. However, the specialized requirements of surgical applications have tended to encourage more specialized designs. For example, laparoscopic surgery and percu￾taneous needle placement procedures typically involve the passage or manipulation of instruments about a com￾mon entry point into the patient’s body. There are two basic design approaches. The first approach uses a pas￾sive wrist to allow the instrument to pivot about the insertion point and has been used in the commercial Aesop and Zeus robots [52.12, 14] as well as several research systems. The second approach mechanically constrains the motion of the surgical tool to rotate about a remote center of motion (RCM) distal to the robot’s structure. In surgery, the robot is positioned so that the RCM point coincides with the entry point into the patient’s body. This approach has been used by the com￾mercially developed daVinci robot [52.2], as well as by numerous research groups, using a variety of kinematic designs [52.15–17]. The emergence of minimally invasive surgery has created a need for robotic systems that can provide high degrees of dexterity in very constrained spaces inside the patient’s body, and at smaller and smaller scales. Figure 52.4 shows several typical examples of current approaches. One common response has been to develop cable-actuated wrists [52.2]. However, a num￾Part F 52.2

Medical Robotics and Computer-Integrated Surgery 52.2 Technology 1205 semiautonomously moving robots for epicardial [52.23] b or endoluminal applications [52.24,25]. Although most surgical robots are mounted to the surgical table,to the operating room ceiling,or to the floor,there has been some interest in developing systems that directly attach to the patient [52.28,29].The main advantage of this approach is that the relative position of 4.2mm the robot and patient is unaffected if the patient moves. The challenges are that the robot must be smaller and that relatively nonintrusive means for mounting it must be developed. Finally,robotic systems intended for use in specific imaging environments pose additional design chal- lenges.First,there is the geometric constraint that the robot (or at least its end-effector)must fit within the scanner along with the patient.Second,the robot's mechanical structure and actuators must not interfere Part F52 with the image formation process.In the case of X- ray and CT,satisfying these constraints is relatively straightforward.The constraints for MRI are more chal- lenging [52.30]. 52.2.2 Control Paradigms Surgical robots assist surgeons in treating patients by moving surgical instruments,sensors,or other devices in relation to the patient.Generally,these motions are controlled by the surgeon in one of three ways: d Preprogrammed,semi-autonomous motion:The de- sired behavior of the robot's tools is specified interactively by the surgeon,usually based on med- ical images.The computer fills in the details and obtains the surgeon's concurrence before the robot is moved.Examples include the selection of needle tar- get and insertion points for percutaneous therapy and Fig.52.4a-d Dexterity enhancement inside a patient's tool cutter paths for orthopaedic bone machining. body:(a)The daVinci wrist with a typical surgical in- Teleoperator control:The surgeon specifies the de- strument (here,scissors)[52.2]:(b)The end-effectors sired motions directly through a separate human of the JHU/Columbia snake telesurgical system [52.18]; interface device and the robot moves immediately. (c)Two-handed manipulation system for use in endogas- Examples include common telesurgery systems such tric surgery [52.26]:(d)five-degree-of-freedom 3 mm wrist as the daVinci [52.2].Although physical master and gripper [52.27]for microsurgery in deep and narrow manipulators are the most common input devices, spaces other human interfaces are also used,notably voice control [52.12]. ber of investigators have investigated other approaches,.Hands-on compliant control:The surgeon grasps the including bending structural elements [52.18],shape- surgical tool held by the robot or a control handle memory alloy actuators [52.19,20],microhydraulic on the robot's end-effector.A force sensor senses systems [52.21],and electroactive polymers [52.22]. the direction that the surgeon wishes to move the Similarly,the problem of providing access to surgical tool and the computer moves the robot to comply sites inside the body has led several groups to develop Early experiences with Robodoc [52.8]and other

Medical Robotics and Computer-Integrated Surgery 52.2 Technology 1205 4.2 mm b) c) d) a) Fig. 52.4a–d Dexterity enhancement inside a patient’s body: (a) The daVinci wrist with a typical surgical in￾strument (here, scissors) [52.2]; (b) The end-effectors of the JHU/Columbia snake telesurgical system [52.18]; (c) Two-handed manipulation system for use in endogas￾tric surgery [52.26]; (d) five-degree-of-freedom 3 mm wrist and gripper [52.27] for microsurgery in deep and narrow spaces ber of investigators have investigated other approaches, including bending structural elements [52.18], shape￾memory alloy actuators [52.19, 20], microhydraulic systems [52.21], and electroactive polymers [52.22]. Similarly, the problem of providing access to surgical sites inside the body has led several groups to develop semiautonomously moving robots for epicardial [52.23] or endoluminal applications [52.24, 25]. Although most surgical robots are mounted to the surgical table, to the operating room ceiling, or to the floor, there has been some interest in developing systems that directly attach to the patient [52.28, 29]. The main advantage of this approach is that the relative position of the robot and patient is unaffected if the patient moves. The challenges are that the robot must be smaller and that relatively nonintrusive means for mounting it must be developed. Finally, robotic systems intended for use in specific imaging environments pose additional design chal￾lenges. First, there is the geometric constraint that the robot (or at least its end-effector) must fit within the scanner along with the patient. Second, the robot’s mechanical structure and actuators must not interfere with the image formation process. In the case of X￾ray and CT, satisfying these constraints is relatively straightforward. The constraints for MRI are more chal￾lenging [52.30]. 52.2.2 Control Paradigms Surgical robots assist surgeons in treating patients by moving surgical instruments, sensors, or other devices in relation to the patient. Generally, these motions are controlled by the surgeon in one of three ways: • Preprogrammed, semi-autonomous motion: The de￾sired behavior of the robot’s tools is specified interactively by the surgeon, usually based on med￾ical images. The computer fills in the details and obtains the surgeon’s concurrence before the robot is moved. Examples include the selection of needle tar￾get and insertion points for percutaneous therapy and tool cutter paths for orthopaedic bone machining. • Teleoperator control: The surgeon specifies the de￾sired motions directly through a separate human interface device and the robot moves immediately. Examples include common telesurgery systems such as the daVinci [52.2]. Although physical master manipulators are the most common input devices, other human interfaces are also used, notably voice control [52.12]. • Hands-on compliant control: The surgeon grasps the surgical tool held by the robot or a control handle on the robot’s end-effector. A force sensor senses the direction that the surgeon wishes to move the tool and the computer moves the robot to comply. Early experiences with Robodoc [52.8] and other Part F 52.2

1206 Part F Field and Service Robotics Fig.52.5a-d Clinically deployed robots for orthopaedic surgery.(a,b) The Robodoc system [52.8.9]repre- sents the first clinically applied robot for joint reconstruction surgery and has been used for both primary and revision hip replacement surgery as well as knee replacement surgery. (c,d)The Acrobot system of Davies et al.[52.31]uses hands-on compliant guiding together with a form of vir- tual fixtures to prepare the femur and tibia for knee replacement surgery Part F52.2 surgical robots [52.16]showed that surgeons found time visual appreciation of deforming anatomy would this form of control to be very convenient and nat-be very difficult. ural for surgical tasks.Subsequently,a number of Teleoperated control provides the greatest versatil- groups have exploited this idea for precise surgical ity for interactive surgery applications,such as dexterous tasks,notably the JHU Steady Hand microsurgical MIS [52.2,12,17,32]or remote surgery [52.33,34].It robot [52.3]shown in Fig.52.3 and the Imperial Col- permits motions to be scaled,and (in some research sys- lege Acrobot orthopaedic system [52.31]shown in tems)facilitates haptic feedback between master and Figs.52.5c,d. slave systems.The main drawbacks are complexity, cost,and disruption to standard operating room work These control modes are not mutually exclusive and flow associated with having separate master and slave are frequently mixed.For example,the Robodoc sys-robots. tem [52.8,9]uses hands-on control to position the Hands-on control combines the precision,strength, robot close to the patient's femur or knee and pre- and tremor-free motion of robotic devices with some programmed motions for bone machining.Similarly,of the immediacy of freehand surgical manipulation. the IBM/JHU LARS robot.[52.16]used both cooper- These systems tend to be less expensive than telesurgical ative and telerobotic control modes.The cooperatively systems,since there is less hardware,and they can be controlled Acrobot [52.31]uses preprogrammed vir- easier to introduce into existing surgical settings.They tual fixtures Sect.52.1.3 derived from the implant exploit a surgeon's natural eye-hand coordination in an shape and its planned position relative to medical intuitively appealing way,and they can be adapted to images. provide force scaling [52.3,4].Although direct motion Each mode has advantages and limitations,depend- scaling is not possible,the fact that the tool moves in the ing on the task.Preprogrammed motions permit complex direction that the surgeon pulls it makes this limitation paths to be generated from relatively simple specifica- relatively unimportant when working with a surgical tions of the specific task to be performed.They are most microscope.The biggest drawbacks are that hands-on often encountered in surgical CAD/CAM applications control is inherently incompatible with any degree of where the planning uses two-(2-D)or three-dimensional remoteness between the surgeon and the surgical tool (3-D)medical images.However,they can also provide and that it is not practical to provide hands-on control of useful macro motions combining sensory feedback in instruments with distal dexterity. teleoperated or hands-on systems.Examples might in- Teleoperation and hands-on control are both com- clude passing a suture or inserting a needle into a vessel patible with shared control modes in which the robot after the surgeon has prepositioned the tip.On the other controller constrains or augments the motions specified hand,interactive specification of motions based on real- by the surgeon,as discussed in Sect.52.2.3

1206 Part F Field and Service Robotics a) c) b) d) Fig. 52.5a–d Clinically deployed robots for orthopaedic surgery. (a,b) The Robodoc system [52.8, 9] repre￾sents the first clinically applied robot for joint reconstruction surgery and has been used for both primary and revision hip replacement surgery as well as knee replacement surgery. (c,d) The Acrobot system of Davies et al. [52.31] uses hands-on compliant guiding together with a form of vir￾tual fixtures to prepare the femur and tibia for knee replacement surgery surgical robots [52.16] showed that surgeons found this form of control to be very convenient and nat￾ural for surgical tasks. Subsequently, a number of groups have exploited this idea for precise surgical tasks, notably the JHU Steady Hand microsurgical robot [52.3] shown in Fig. 52.3 and the Imperial Col￾lege Acrobot orthopaedic system [52.31] shown in Figs. 52.5c,d. These control modes are not mutually exclusive and are frequently mixed. For example, the Robodoc sys￾tem [52.8, 9] uses hands-on control to position the robot close to the patient’s femur or knee and pre￾programmed motions for bone machining. Similarly, the IBM/JHU LARS robot. [52.16] used both cooper￾ative and telerobotic control modes. The cooperatively controlled Acrobot [52.31] uses preprogrammed vir￾tual fixtures Sect. 52.1.3 derived from the implant shape and its planned position relative to medical images. Each mode has advantages and limitations, depend￾ing on the task. Preprogrammed motions permit complex paths to be generated from relatively simple specifica￾tions of the specific task to be performed. They are most often encountered in surgical CAD/CAM applications where the planning uses two- (2-D) or three-dimensional (3-D) medical images. However, they can also provide useful macro motions combining sensory feedback in teleoperated or hands-on systems. Examples might in￾clude passing a suture or inserting a needle into a vessel after the surgeon has prepositioned the tip. On the other hand, interactive specification of motions based on real￾time visual appreciation of deforming anatomy would be very difficult. Teleoperated control provides the greatest versatil￾ity for interactive surgery applications, such as dexterous MIS [52.2, 12, 17, 32] or remote surgery [52.33, 34]. It permits motions to be scaled, and (in some research sys￾tems) facilitates haptic feedback between master and slave systems. The main drawbacks are complexity, cost, and disruption to standard operating room work flow associated with having separate master and slave robots. Hands-on control combines the precision, strength, and tremor-free motion of robotic devices with some of the immediacy of freehand surgical manipulation. These systems tend to be less expensive than telesurgical systems, since there is less hardware, and they can be easier to introduce into existing surgical settings. They exploit a surgeon’s natural eye–hand coordination in an intuitively appealing way, and they can be adapted to provide force scaling [52.3, 4]. Although direct motion scaling is not possible, the fact that the tool moves in the direction that the surgeon pulls it makes this limitation relatively unimportant when working with a surgical microscope. The biggest drawbacks are that hands-on control is inherently incompatible with any degree of remoteness between the surgeon and the surgical tool and that it is not practical to provide hands-on control of instruments with distal dexterity. Teleoperation and hands-on control are both com￾patible with shared control modes in which the robot controller constrains or augments the motions specified by the surgeon, as discussed in Sect. 52.2.3. Part F 52.2

Medical Robotics and Computer-Integrated Surgery 52.2 Technology 1207 52.2.3 Virtual Fixtures and Human-Machine Cooperative Situation assessment Task strategy and decisions Systems Sensory-motor coordination Although one goal of both teleoperation and hands-on Display control is often transparency,i.e.,the ability to move an instrument with the freedom and dexterity ne might Sensors expect with a handheld tool,the fact that a computer Online references and decision report is actually controlling the robot's motion creates many Manipulation more possibilities.The simplest is a safety barrier or enhancement no-fly zone,in which the robot's tool is constrained from Atlases 年Cooperative control entering certain portions of its workspace.More so- HMCS system and“macros Libraries phisticated versions include virtual springs,dampers,or complex kinematic constraints that help a surgeon align Fig.52.6 Human-machine cooperative systems(HMCS)in surgery a tool,maintain a desired force,or maintain a desired anatomical relationship.The Acrobot system shown in Registered model Constraint Figs.52.5c,d represents a successful clinical application generation of the concept,which has many names,of which vir- tual fixtures seems to be the most popular [52.35,361. A number of groups are exploring extensions of the con- cept to active cooperative control,in which the surgeon Path minW(Jp△q-△Pae,)l2 and robot share or trade off control of the robot during △q a surgical task or subtask.As the ability of computers to Tool tip guidance △Pae Subject to model and follow along surgical tasks improves,these virtual fixture G△q2g modes will become more and more important in sur- gical assistant applications.Figure 52.6 illustrates the overall concept of human-machine cooperative systems State in surgery,and Fig.52.7 illustrates the use of registered anatomical models to generate constraint-based virtual Fig.52.7 Human-machine cooperative manipulation using con- fixtures.These approaches are equally valid whether the straint-based virtual fixtures,in which patient-specific constraints surgeon interacts with the system through classical tele- are derived from registered anatomical models [52.35] operation or through hands-on compliant control.See also Chap.31. quire a careful and rigorous development process with Both teleoperation and hands-on control are like- extensive documentation at all stages of design,im- wise used in human-machine cooperative systems for plementation,testing,manufacturing,and field support rehabilitation and disability assistance systems.Con- Generally,systems should have extensive redundancy strained hands-on systems offer special importance for built into hardware and control software,with mul- rehabilitation applications and for helping people with tiple consistency conditions constantly enforced.The movement disorders.Similarly,teleoperation and intel-basic consideration is that no single point of failure ligent task following and control are likely to be vital should cause the robot to go out of control or to in- for further advances in assistive systems for people with jure a patient.Although there is some difference of severe physical disabilities.See Chap.53 for a further opinion as to the best way to make trade-offs,medical discussion of human-machine cooperation in assistive manipulators are usually equipped with redundant posi- systems tion encoders and ways to mechanically limit the speed and/or force that the robot can exert.If a consistency 52.2.4 Safety and Sterility check failure is detected,two common approaches are to freeze robot motion or to cause the manipulator to go Medical robots are safety-critical systems,and safety limp.Which is better depends strongly on the particular should be considered from the very beginning of the application. design process [52.37,38].Although there is some Sterilizability and biocompatibility are also crucial difference in detail,government regulatory bodies re- considerations.Again,the details are application de-

Medical Robotics and Computer-Integrated Surgery 52.2 Technology 1207 52.2.3 Virtual Fixtures and Human–Machine Cooperative Systems Although one goal of both teleoperation and hands-on control is often transparency, i. e., the ability to move an instrument with the freedom and dexterity ne might expect with a handheld tool, the fact that a computer is actually controlling the robot’s motion creates many more possibilities. The simplest is a safety barrier or no-fly zone, in which the robot’s tool is constrained from entering certain portions of its workspace. More so￾phisticated versions include virtual springs, dampers, or complex kinematic constraints that help a surgeon align a tool, maintain a desired force, or maintain a desired anatomical relationship. The Acrobot system shown in Figs. 52.5c,d represents a successful clinical application of the concept, which has many names, of which vir￾tual fixtures seems to be the most popular [52.35, 36]. A number of groups are exploring extensions of the con￾cept to active cooperative control, in which the surgeon and robot share or trade off control of the robot during a surgical task or subtask. As the ability of computers to model and follow along surgical tasks improves, these modes will become more and more important in sur￾gical assistant applications. Figure 52.6 illustrates the overall concept of human–machine cooperative systems in surgery, and Fig. 52.7 illustrates the use of registered anatomical models to generate constraint-based virtual fixtures. These approaches are equally valid whether the surgeon interacts with the system through classical tele￾operation or through hands-on compliant control. See also Chap. 31. Both teleoperation and hands-on control are like￾wise used in human–machine cooperative systems for rehabilitation and disability assistance systems. Con￾strained hands-on systems offer special importance for rehabilitation applications and for helping people with movement disorders. Similarly, teleoperation and intel￾ligent task following and control are likely to be vital for further advances in assistive systems for people with severe physical disabilities. See Chap. 53 for a further discussion of human–machine cooperation in assistive systems. 52.2.4 Safety and Sterility Medical robots are safety-critical systems, and safety should be considered from the very beginning of the design process [52.37, 38]. Although there is some difference in detail, government regulatory bodies re￾Situation assessment Task strategy and decisions Sensory-motor coordination HMCS system • Display • Sensors • Online references and decision report • Manipulation enhancement • Cooperative control and “macros” Atlases Libraries Fig. 52.6 Human–machine cooperative systems (HMCS) in surgery State Constraint generation Robot interface min||W (Jtip Δq – ΔPdes)||2 Subject to GΔq≥g Δq ΔPdes Registered model Tool tip guidance virtual fixture Path Fig. 52.7 Human–machine cooperative manipulation using con￾straint-based virtual fixtures, in which patient-specific constraints are derived from registered anatomical models [52.35] quire a careful and rigorous development process with extensive documentation at all stages of design, im￾plementation, testing, manufacturing, and field support. Generally, systems should have extensive redundancy built into hardware and control software, with mul￾tiple consistency conditions constantly enforced. The basic consideration is that no single point of failure should cause the robot to go out of control or to in￾jure a patient. Although there is some difference of opinion as to the best way to make trade-offs, medical manipulators are usually equipped with redundant posi￾tion encoders and ways to mechanically limit the speed and/or force that the robot can exert. If a consistency check failure is detected, two common approaches are to freeze robot motion or to cause the manipulator to go limp. Which is better depends strongly on the particular application. Sterilizability and biocompatibility are also crucial considerations. Again, the details are application de￾Part F 52.2

1208 Part F Field and Service Robotics pendent.Common sterilization methods include gamma Medical image segmentation and image fusion to rays (for disposable tools),autoclaving,soaking or gas construct and update patient-specific anatomic mod- sterilization,and the use of sterile drapes to cover un- els sterile components.Soaking or gas sterilization are less Biomechanical modeling for analyzing and pre- likely to damage robot components,but very rigorous dicting tissue deformations and functional factors cleaning is required to prevent extraneous foreign matter affecting surgical planning,control,and rehabilita- from shielding microbes from the sterilizing agent. tion Careful attention to higher levels of application pro- ● Optimization methods for treatment planning and tocols is also essential.Just like any other tool,surgical interactive control of systems robots must be used correctly by surgeons,and care- Methods for registering the virtual realiry of images ful training is essential for safe practice.Surgeons must and computational models to the physical realiry of understand both the capabilities and limitations of the an actual patient system.In surgical CAD/CAM applications,the sur- Methods for characterizing treatment plans and indi- Part geon must understand how the robot will execute the vidual task steps such as suturing,needle insertion, plan and be able to verify that the plan is being fol- or limb manipulation for purposes of planning,mon- 可 lowed.If the surgeon is interactively commanding the itoring,control,and intelligent assistance robot,it is essential that the robot interpret these com- Real-time data fusion for such purposes as updating mands correctly.Similarly,it is essential that the robot's models from intraoperative images model of its task environment correspond correctly to Methods for human-machine communication,in- the actual environment.Although careful design and im- cluding real-time visualization of data models, plementation can practically eliminate the likelihood of natural language understanding,gesture recognition, a runaway condition by the manipulator,this will do little etc. good if the robot is badly registered to the patient im- Methods for characterizing uncertainties in data, ages used to control the procedure.If the robot fails for models,and systems and for using this information any reason,there must be well-documented and planned in developing robust planning and control methods procedures for recovery (and possibly continuing the procedure manually). An in-depth examination of this research is beyond the Finally,it is important to remember that a well- scope of this article.A more complete discussion of these designed robot system can actually enhance patient topics may be found in the suggested further reading in safety.The robot is not subject to fatigue or momen- Sect.52.4. tary lapses of attention.Its motions can be more precise and there is less chance that a slip of the scalpel may 52.2.6 Registration damage some delicate structure.In fact,the system can be programmed to provide virtual fixtures(Sect.52.2.3) Geometric relationships are fundamental in medical preventing a tool from entering a forbidden region unless robotics,especially in surgical CAD/CAM.There is the surgeon explicitly overrides the system. an extensive literature on techniques for coregistering coordinate systems associated with robots,sensors,im- 52.2.5 Imaging and Modeling of Patients ages,and the patient [52.39,40].Following [52.40],we briefly summarize the main concepts here.Suppose that As the capabilities of medical robots continue to evolve, we have coordinates the use of computer systems to model dynamically changing patient-specific anatomy will become increas- A=(xA,yA,ZA) ingly important.There is a robust and diverse research 唱=(xB,yB,B), community addressing a very broad range of research topics.including the creation of patient-specific mod- corresponding to comparable locations in two coor- els from medical images,techniques for updating these dinate systems RefA and RefB.Then the process of models based upon real-time image and other sensor registration is simply that of finding a function TAB(...) data,and the use of these models for planning and mon- such that itoring of surgical procedures.Some of the pertinent research topics include the following: UB TAB(vA)

1208 Part F Field and Service Robotics pendent. Common sterilization methods include gamma rays (for disposable tools), autoclaving, soaking or gas sterilization, and the use of sterile drapes to cover un￾sterile components. Soaking or gas sterilization are less likely to damage robot components, but very rigorous cleaning is required to prevent extraneous foreign matter from shielding microbes from the sterilizing agent. Careful attention to higher levels of application pro￾tocols is also essential. Just like any other tool, surgical robots must be used correctly by surgeons, and care￾ful training is essential for safe practice. Surgeons must understand both the capabilities and limitations of the system. In surgical CAD/CAM applications, the sur￾geon must understand how the robot will execute the plan and be able to verify that the plan is being fol￾lowed. If the surgeon is interactively commanding the robot, it is essential that the robot interpret these com￾mands correctly. Similarly, it is essential that the robot’s model of its task environment correspond correctly to the actual environment. Although careful design and im￾plementation can practically eliminate the likelihood of a runaway condition by the manipulator, this will do little good if the robot is badly registered to the patient im￾ages used to control the procedure. If the robot fails for any reason, there must be well-documented and planned procedures for recovery (and possibly continuing the procedure manually). Finally, it is important to remember that a well￾designed robot system can actually enhance patient safety. The robot is not subject to fatigue or momen￾tary lapses of attention. Its motions can be more precise and there is less chance that a slip of the scalpel may damage some delicate structure. In fact, the system can be programmed to provide virtual fixtures (Sect. 52.2.3) preventing a tool from entering a forbidden region unless the surgeon explicitly overrides the system. 52.2.5 Imaging and Modeling of Patients As the capabilities of medical robots continue to evolve, the use of computer systems to model dynamically changing patient-specific anatomy will become increas￾ingly important. There is a robust and diverse research community addressing a very broad range of research topics, including the creation of patient-specific mod￾els from medical images, techniques for updating these models based upon real-time image and other sensor data, and the use of these models for planning and mon￾itoring of surgical procedures. Some of the pertinent research topics include the following: • Medical image segmentation and image fusion to construct and update patient-specific anatomic mod￾els • Biomechanical modeling for analyzing and pre￾dicting tissue deformations and functional factors affecting surgical planning, control, and rehabilita￾tion • Optimization methods for treatment planning and interactive control of systems • Methods for registering the virtual reality of images and computational models to the physical reality of an actual patient • Methods for characterizing treatment plans and indi￾vidual task steps such as suturing, needle insertion, or limb manipulation for purposes of planning, mon￾itoring, control, and intelligent assistance • Real-time data fusion for such purposes as updating models from intraoperative images • Methods for human–machine communication, in￾cluding real-time visualization of data models, natural language understanding, gesture recognition, etc. • Methods for characterizing uncertainties in data, models, and systems and for using this information in developing robust planning and control methods An in-depth examination of this research is beyond the scope of this article. A more complete discussion of these topics may be found in the suggested further reading in Sect. 52.4. 52.2.6 Registration Geometric relationships are fundamental in medical robotics, especially in surgical CAD/CAM. There is an extensive literature on techniques for coregistering coordinate systems associated with robots, sensors, im￾ages, and the patient [52.39, 40]. Following [52.40], we briefly summarize the main concepts here. Suppose that we have coordinates vr A = (xA, yA,zA) vr B = (xB, yB,zB) , corresponding to comparable locations in two coor￾dinate systems RefA and RefB. Then the process of registration is simply that of finding a function TAB(···) such that vB = TAB(vA) . Part F 52.2